Large surface potential of Alq3 film and its decay -: art. no. 023703

The surface potential across Alq(3) [tris(8-quinolinolato)aluminum] evaporated films on a metal (Au, Al) electrode was measured by the Kelvin probe method and the results were discussed taking into account the orientational ordering of Alq(3) molecules, the presence of surface charges on Alq(3) films and the displacement of excess charge (electrons and holes) from the electrode into Alq(3) films. The very large surface potential established in as-deposited Alq(3) films was mainly due to the alignment of dipoles of Alq(3) molecules, whereas the small surface potential that remained in the films after photoirradiation was due to excess charge. In order to clarify the drastic decrease of surface potential by photoirradiation, the surface potential decay was examined. (C) 2005 American Institute of Physics.